Field of the Invention
The present invention relates to a power supply device, and more particularly, to a switching power supply device that generates a plurality of output power supply voltages while retaining a small footprint.
Description of the Related Art
A positive/negative power supply generation device for generating a positive power supply and a negative power supply from a single power supply is described, for instance, in Japanese Unexamined Patent Publication No. 2003-186552. During a first time period, the positive/negative power supply generation device charges electrical power into an inductor and then discharges the charged electrical power to a positive power supply capacitor through a first diode. During a subsequent time period, the positive/negative power supply generation device charges electrical power again into the inductor and then discharges the charged electrical power to a negative power supply capacitor through a second diode.
A switching regulator capable of outputting both an arbitrary positive voltage and an arbitrary negative voltage without regard to an input voltage is described in Japanese Unexamined Patent Publication No. 2009-5442. The switching regulator charges electrical power into an inductor, and then discharges the charged electrical power to a negative voltage capacitor through a third switch and at the same time discharges the charged electrical power to a positive voltage capacitor through a fourth switch. During this discharge period, one end of the inductor is coupled to the negative voltage capacitor through the third switch in the ON state and the other end of the inductor is coupled to the negative voltage capacitor through the fourth switch in the ON state.